Davies played club rugby for Cardiff RFC and London Welsh. He captained Cardiff for three seasons in the 1970s, his most famous game for Cardiff probably being a 1977–8 Welsh Cup game against Pontypool when he scored four tries (beating his marker and near namesake Gareth Davies on each occasion) to earn his side a 16–11 win.

He made his international debut on Saturday, 3 December 1966 against Australia in Cardiff, where Wales lost 14–11 – he was to face the Wallabies again in his final appearance for Wales in 1978, this time in Sydney, and again a loss. All in all, he was capped 46 times for his country. He was switched from his original position of centre to the right wing by Wales coach Clive Rowlands on their 1969 tour of Australia and New Zealand, and thereafter played in that position.

Davies toured with the British Lions in 1968 and 1971 and was part of the group of Welsh Seventies legends, ranking in rugby history alongside Gareth Edwards, Barry John, JPR Williams, Phil Bennett and Bobby Windsor. A superb attacking player, he has been called one of the best wingers rugby has ever seen. Davies is best remembered for his try – one of 20 in 46 Tests – in the 1971 Five Nations match against Scotland. The Scots were leading before Davies scored in the corner in the last minute. Backrower John Taylor then kicked his famous conversion to steal victory.

Invited to join the 1974 Lions Tour of South Africa, he turned the opportunity down on his personal uncomfortable position at the consequences and realities of apartheid.[5]

For Wales: 46 Internationals, of which Wales won 29, lost 14 and drew 3 (points for 758, points against 507). 20 tries, 8 of them before the value of a try was raised to four points in the 1971–72 season (72 points in all).

For the British Lions: 5 Internationals of which the Lions won two, lost two and drew one (points for 54, points against 53). Davies scored three tries for the Lions during Test games, all of them on the 1971 tour to New Zealand (9 points).[6]

After retiring as a player, Davies became a journalist, writing on rugby matters for The Times. He sat on Tasker Watkins committee to reform Welsh rugby. He became chairman of the Wales Youth Agency, and his commitment to youth work earned him a CBE in 2002.[7]